PT-141

A small ring-shaped peptide, seven amino acids long, injected under the skin shortly before sex. It is an approved prescription medicine in the United States under the brand name Vyleesi, and only for one thing: low sexual desire that causes real distress, in women who have not been through the menopause. The sequence field is deliberately left empty. The chain is Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys)-OH: it opens with norleucine, which has no letter in the standard one-letter code, it contains phenylalanine in its mirror-image D form, its ends are capped with an acetyl group and a free acid, and the chain is closed into a ring by a bond between the second and seventh building blocks. A plain one-letter string would describe a different, straight-chain molecule. PubChem gives C50H68N14O10 and 1,025.2 g/mol (CID 9941379), which matches the approved product information exactly.

Sold as

Injection under the skin of the belly or thigh, as needed, at least 45 minutes before sex. No more than one dose in 24 hours; the label says more than 8 doses a month is not recommended.

Legal status in the EU

Not an approved medicine in the EU. The European Commission's Union Register of medicinal products — the file of every centrally authorised human medicine, updated 31 July 2026 — contains no bremelanotide and no Vyleesi, and the European Medicines Agency has published no assessment of it: no approval, no refusal and no withdrawn application. That is a different situation from a medicine Europe examined and turned down; here there is no European file at all, so anything sold as PT-141 in Europe is an unlicensed product whatever the seller calls it. In the United States it has been an approved prescription medicine since 21 June 2019 (NDA 210557), currently marketed by Cosette Pharmaceuticals. It is NOT prohibited in sport: the WADA 2026 Prohibited List does not name bremelanotide, PT-141, melanotan or melanocortin anywhere in its text, and section S0 cannot capture it either, because S0 applies only to substances with no current approval by any governmental regulatory health authority. Melanotan II, nearly the same molecule, would be caught by S0 precisely because it has never been approved anywhere.

It switches on melanocortin receptors, which the body normally uses for pigment and appetite signalling, most strongly MC1R and then MC4R. MC4R sits on nerve cells throughout the brain and spinal cord, so this is a brain drug rather than a blood-flow drug. In the only study to look directly, women scanned after a dose responded differently to erotic video than after a dummy injection, with less activity in a region that handles self-monitoring of touch and stronger linking between the amygdala and the insula, which the researchers read as the drug quietening self-consciousness and sensitising the women to what they were watching. MC1R activity on pigment cells is why it darkens patches of skin. The approved label states in as many words that the mechanism by which it helps this condition is unknown. The compound itself does not linger: peak levels come about an hour after the injection and half a dose has cleared in about 2.7 hours.

Part of the bodyWhat happensHow it is knownKind of evidence

Sexual desire, and how much the lack of it bothers you

This is the one thing it is approved for, and the effect is real and small. Over six months, women injecting it before sex scored higher on a two-question desire scale than women injecting a dummy, and reported being less bothered by their low desire. On the desire scale, which runs from 1.2 to 6, the average rise was 0.54 against 0.24 on the dummy injection in the first trial and 0.63 against 0.21 in the second. On the bother scale, which runs from 0 to 4, the average fall was 0.73 against 0.36, and 0.71 against 0.42. The difference showed up by week 4 and did not grow much after that.

Measured in two identical randomised trials with dummy-injection groups, 1,267 premenopausal women in total, 24 weeks each, neither the women nor the staff knowing which injection they had. The figures above are the two arms as posted to the trial registry.

Measured in people

Source [03]Source [04]Source [05]

Your sex life, as counted rather than scored

Nothing measurable happened. The trials counted how many sexual encounters within 16 hours of an injection the women called satisfying, and the count did not change: no better than the dummy injection in either trial. This matters more than it looks, because that same count had been the main measure of the earlier dose-finding trial, which randomised 397 women, and there it did rise more on the drug than on the dummy. When the co-primary measures were switched to the desire and distress questionnaires before the big trials were unblinded, and the count became a secondary measure, it stopped separating from placebo. The US regulator's position is that it does not require this measure to improve, because it is not part of how the condition is diagnosed.

Counted in the same 1,202 women whose questionnaire scores are reported above, over 24 weeks, and separately in the 397 women randomised in the earlier dose-finding trial over 12 weeks.

Measured in people

Source [03]Source [06]Source [14]

The stomach

Feeling sick is the single commonest thing that happens, and it is not a small effect: 40 per cent of women on the drug against about 1 per cent on the dummy injection. It starts within half an hour to an hour of the injection and lasts about two hours. It is worst the first time — 21 per cent of women were sick after their first dose, then about 3 per cent after later ones. Thirteen per cent of women needed an anti-sickness medicine. The drug also slows the stomach down, which is why the label warns it can delay other tablets from being absorbed.

Counted in 627 women given bremelanotide and 620 given a dummy injection across the two randomised trials, and reported in the approved US product information.

Measured in people

Source [01]Source [03]

Blood pressure and heart rate

Blood pressure goes up a little after every dose and the heart slows a little. In the trials the biggest average rises were 6 mmHg for the top number and 3 mmHg for the bottom one, peaking two to four hours after the injection, with the pulse dropping by up to 5 beats a minute. It settles back to normal within about 12 hours. That is small in a healthy person, and it is the reason the medicine is forbidden outright to anyone with uncontrolled high blood pressure or known heart disease, and not recommended for anyone at high risk of it.

Measured in the two randomised trials, and separately in a dedicated study in which 127 premenopausal women wore a 24-hour blood pressure monitor while taking a dose every day for 8 days. That study was open — everyone knew what they were taking — and compared each woman with her own starting readings rather than with a placebo group.

Measured in people

Source [01]Source [06]

Skin colour, and the gums

It darkens patches of skin, because one of the switches it flips is the same one the body uses to make a tan. Used the way the label allows — no more than 8 doses a month — this happened to 1 per cent of women and to nobody on the dummy injection, on the face, the gums and the breasts. Used daily, it becomes far more common: in a separate study, 38 per cent of women developed darkened patches after 8 days in a row, and another 14 per cent of those who carried on for 8 more days developed new ones. Women with darker skin were more likely to get it. The label states plainly that the patches were not confirmed to fade in everyone after stopping.

Counted in 627 women on bremelanotide and 620 on a dummy injection in the two randomised trials, and in a separate daily-dosing study reported in the approved US product information.

Measured in people

Source [01]Source [08]

Other tablets you swallow

It slows the stomach, so tablets taken around the same time can be absorbed more slowly and less completely. The label singles out two. Naltrexone taken by mouth, used to treat alcohol and opioid addiction, can drop far enough that the label says not to combine them at all, because the consequences of that treatment failing are severe. Indomethacin, a painkiller, is also affected. The label tells people to avoid the injection when taking oral antibiotics or anything else that needs to reach a threshold level to work.

Measured in dedicated drug-interaction studies submitted with the US application and summarised in the approved product information.

Measured in people

Source [01]

The brain

The compound does not work on blood flow to the genitals the way the erection drugs do. It switches on a receptor called MC4R, which sits on nerve cells in the parts of the brain that handle appetite, arousal and body awareness. In the only study to look directly, women with low desire were scanned twice, once after the drug and once after a dummy injection, without knowing which. After the drug their brains responded differently to erotic video: more activity in the cerebellum and the movement-planning area, less in a region that handles self-monitoring of touch, and stronger linking between the amygdala and the insula. The researchers read that as the drug quietening self-consciousness and making the women more responsive to what they were watching. The label itself says the mechanism by which it helps is unknown.

One randomised, double-blind crossover study in which 31 premenopausal women with low sexual desire each received both bremelanotide and a dummy injection on separate days, with brain scans after each. Funded by the manufacturer together with two UK public research funders.

One small study

Source [01]Source [09]

Hormones in the blood

Small movements, of unclear meaning. In the same 31-woman scanning study, a single injection produced small rises in two pituitary hormones, LH and FSH, and in testosterone, with no change in oestrogen or progesterone. Nobody has shown that these movements have anything to do with the change in desire, and no larger study has measured them.

Blood measured in 31 premenopausal women who each received both the drug and a dummy injection on separate days.

One small study

Source [09]

Erections, in men

This is where the compound started, and it never finished. In the early 2000s it was given as a nasal spray to healthy men and to men with erectile dysfunction, and a device that measures rigidity recorded more erectile activity than after a dummy spray at doses above 7 milligrams. A separate study injected it under the skin of men who had not responded well to Viagra and recorded the same kind of effect. Those studies measured a device reading over a few hours in a clinic, not whether anyone's sex life changed, and none of them was a trial of the kind that leads to approval. The application to go on testing it in men in the United States was withdrawn in 2017, and no product ever came of it. The register found no registered trial of bremelanotide for a sexual problem in men.

Two double-blind placebo-controlled dose-ranging studies in healthy men and men with erectile dysfunction, published in 2004, with erections measured by a rigidity monitor. The withdrawal of the male application is recorded in the FDA's own review of the female application.

One small study

Source [06]Source [15]Source [16]

Two identical randomised, dummy-controlled trials, which between them randomised 1,267 premenopausal women, met both of their pre-specified main measures and missed their key secondary one. On a desire questionnaire running from 1.2 to 6, scores rose 0.54 against 0.24 on the dummy injection in study 301 and 0.63 against 0.21 in study 302 (p=0.0002 and p<0.0001); on a 0-to-4 scale of how much the low desire bothered them, scores fell 0.73 against 0.36 and 0.71 against 0.42 (p<0.0001 and p=0.0053). Asked directly whether the treatment had helped, 58.3 and 58.2 per cent said yes against 36.1 and 35.4 per cent on the dummy injection. The number of satisfying sexual encounters did not move at all (0.0 against -0.1, p=.764; 0.0 against 0.0, p=.702), which collapsed the rest of the ranked secondary measures into exploratory ones — and that count had been the primary measure of the earlier dose-finding trial, which randomised 397 women, where it did separate from placebo. Three further facts belong beside the win. The US regulator's own reviewers concluded that a 1.2-point change on the desire scale was the appropriate threshold for a meaningful improvement, not the 0.6 the manufacturer proposed, and the average woman improved by 0.5 to 0.6; the review's summary word for the benefit is "modest". Forty per cent of the bremelanotide group left the 24-week blind period early against 13 per cent of the placebo group in study 1 (39 against 25 per cent in study 2), with 18 per cent against 2 per cent stopping specifically for side effects. And when the blind period ended, 70 per cent of the bremelanotide group chose to enter the open-label year against 87 per cent of the placebo group — the manufacturer's own figure, which a peer-reviewed re-analysis in the Journal of Sex Research turns into the argument that participants preferred placebo, and which the trial authors dispute in a published rebuttal. The sequence field is null because the molecule is a cyclic heptapeptide containing D-phenylalanine and norleucine with an acetylated N-terminus, none of which the standard one-letter code can express.

It is a same-day drug. Peak levels in the blood come about an hour after the injection, half of a dose has cleared in about 2.7 hours, and essentially all of what is injected reaches the bloodstream. The label says to inject at least 45 minutes before sex and states plainly that the duration of the effect after each dose is unknown and the best moment to inject has not been fully worked out. Sickness, if it comes, starts within half an hour to an hour and lasts about two hours. Blood pressure peaks two to four hours in and is back to normal within about twelve. In the one study that asked, more women reported higher desire a full day after the injection than after a dummy one. Across the trials, the difference on the monthly questionnaires appeared by week 4 and did not grow much over the remaining five months — which is why the label tells doctors to stop after 8 weeks if the woman reports no improvement.

What was measuredWhat happenedIn whomHow it is known

Sexual desire, on a 1.2-to-6 questionnaire scale

Rose 0.54 against 0.24 on a dummy injection in the first trial, and 0.63 against 0.21 in the second. Both differences were statistically solid (p=0.0002 and p<0.0001). The middle woman on the drug improved by 0.6 and the middle woman on the dummy injection by 0. Everyone started around 2.0 to 2.1.

1,202 premenopausal women with acquired, generalised low sexual desire causing distress, average age 39, in a relationship for an average of 12 years, 24 weeks. 86 per cent white, 97 per cent recruited in the United States.

Measured in people

Source [01]Source [04]Source [05]

How much the low desire bothered them, on a 0-to-4 scale

Fell 0.73 against 0.36 on a dummy injection in the first trial and 0.71 against 0.42 in the second (p<0.0001 and p=0.0053). The middle woman on the drug improved by a full point and the middle woman on the dummy injection by none. Everyone started around 2.8 to 2.9.

The same 1,202 women, 24 weeks. The question asked was: how often did you feel bothered by low sexual desire.

Measured in people

Source [01]Source [04]Source [05]

How many women said the treatment had helped them

58.3 per cent and 58.2 per cent of women on bremelanotide against 36.1 per cent and 35.4 per cent on the dummy injection, in the two trials. So roughly 6 in 10 said it helped, and roughly 3.5 in 10 said the same about an injection with nothing in it. The gap of about 22 percentage points is the clearest single number in the whole programme, and the placebo figure beside it is the reason a mean change and a responder count tell different stories.

The 1,202 women in the two randomised trials, answering a question about how much benefit they felt from the study drug at the end of 24 weeks. The threshold for counting as helped was set by an independent committee before the results were unblinded.

Measured in people

Source [03]

Satisfying sexual encounters, counted

No difference. In the first trial the change was 0.0 on bremelanotide and -0.1 on the dummy injection (p=.764); in the second, 0.0 and 0.0 (p=.702); pooled, 0.0 and -0.1 (p=.630). Because this was the ranked key secondary measure and it failed, everything below it in the trials' own hierarchy became exploratory.

The same 1,202 women, counting encounters within 16 hours of a dose and reported within 72 hours, over 24 weeks.

Measured in people

Source [03]Source [04]

People who left the trial early

Far more on the drug. Of the women being analysed for effect, 40 per cent on bremelanotide left the 24-week blind period early against 13 per cent on the dummy injection in the first trial, and 39 against 25 per cent in the second. Stopping specifically because of a side effect happened to 18 per cent on the drug and 2 per cent on the dummy injection; sickness alone accounted for 8 per cent on the drug and none on the dummy.

The 1,247 women in the safety analysis and the 1,202 in the efficacy analysis across the two randomised trials, 24 weeks.

Measured in people

Source [01]Source [07]

Choosing to carry on for another year

70 per cent of the women who had been on bremelanotide went into the optional open-label year, against 87 per cent of the women who had been on the dummy injection. That is the manufacturer's own figure. Of the 684 women who did enrol, 272 finished the year.

856 women who completed the 24-week blind period of the two randomised trials and were offered a further 52 weeks in which everyone received bremelanotide and knew it.

Measured in people

Source [08]Source [17]

Feeling sick

40.0 per cent of women against 1.3 per cent on a dummy injection. Vomiting, 4.8 per cent against 0.2 per cent. Thirteen per cent needed an anti-sickness medicine, and 8 per cent left the trial because of the sickness against nobody on the dummy injection.

627 women given bremelanotide and 620 given a dummy injection across the two randomised trials, 24 weeks.

Measured in people

Source [01]

Flushing, headache and reactions where the needle goes in

Flushing 20.3 per cent against 0.3 per cent on a dummy injection; headache 11.3 against 1.9; injection-site reactions 13.2 against 8.4; pins and needles 2.6 against 0.0; dizziness 2.2 against 0.5.

627 women given bremelanotide and 620 given a dummy injection across the two randomised trials, 24 weeks.

Measured in people

Source [01]

Whether the questionnaires measured anything that matters

Contested in print, and never settled. Two peer-reviewed re-analyses in the Journal of Sex Research argue that the desire and distress scales used as the main measures have thin evidence of validity in women with this diagnosis, that most of the outcomes listed on the trial registry were never published, and that the effects on the ones that were published are small. The trial authors published a rebuttal in the same journal. Separately, the US regulator's own reviewers disagreed with the manufacturer about the threshold for a meaningful change on the desire scale: the manufacturer proposed 0.6 points and the regulator concluded 1.2 was more appropriate. The average woman on the drug improved by 0.5 to 0.6.

Re-analyses of the published and registry data from the same 1,202 women, plus the regulator's review of the manufacturer's anchor studies and patient exit interviews.

Studies in people disagree

Source [06]Source [19]Source [20]

Blood pressure, measured over a whole day

Daytime blood pressure rose on average by 1.9 mmHg for the top number (95 per cent confidence interval 1.0 to 2.7) and 1.7 for the bottom (0.9 to 2.4) after 8 days of daily dosing, with the pulse falling by half a beat a minute. Readings 12 to 24 hours after a dose were back to where they started. There was no dummy-injection group in this study: each woman was compared with her own readings before starting.

127 premenopausal women who completed an open-label study wearing a 24-hour blood pressure monitor, dosing once daily for 8 days. Only 2 of them had treated high blood pressure.

One small study

Source [01]Source [06]

Desire in the 24 hours after a single injection

21 of 31 women said their desire had increased in the day after the bremelanotide injection, against 8 of the same 31 after the dummy injection. Three said yes to both and five said no to both. Because every woman had both injections, this is as close to a fair comparison as a study this size can get.

31 premenopausal women with low sexual desire, each given both bremelanotide 1.75 mg and a dummy injection on separate days, neither they nor the researchers knowing which was which.

One small study

Source [09]Source [18]

Feeling sick is the dominant effect: 40 per cent of women against 1.3 per cent on a dummy injection, starting within an hour and lasting about two, requiring an anti-sickness medicine in 13 per cent and driving 8 per cent out of the trials against nobody on the dummy. Flushing affected 20.3 per cent against 0.3, headache 11.3 against 1.9, injection-site reactions 13.2 against 8.4, vomiting 4.8 against 0.2. Blood pressure rises after every dose — up to 6 mmHg on the top number and 3 on the bottom, with the pulse falling up to 5 beats a minute, settling within about 12 hours — which is why it is contraindicated outright in uncontrolled high blood pressure and in known cardiovascular disease, and not recommended for anyone at high cardiovascular risk. It darkens patches of skin, gums and breasts: 1 per cent at label dosing against nobody on the dummy injection, but 38 per cent after 8 consecutive daily doses in a study with no comparison group, more often in women with darker skin, and the label states resolution was not confirmed in all patients after stopping. One woman in the whole programme developed acute liver inflammation with liver enzymes over 40 times the upper limit of normal, which resolved four months after stopping and whose cause could not be established. In pregnant dogs, losses after implantation ran three to eight times higher than in controls at every dose tested and no safe dose could be identified, so women are told to use effective contraception and to stop if pregnancy is suspected. It must not be combined with naltrexone taken by mouth for addiction, whose levels it can push down far enough for that treatment to fail.

EffectWhat it feels likeHow often

Dark patches on the skin and gumsSerious

The same switch that raises desire also tells pigment cells to make melanin, so patches darken — face, gums and breasts are the places named in the label. Darker skin makes it more likely. The label says resolution was not confirmed in all patients after stopping, which is the closest thing in this record to a permanent effect, and it is why the label says more than 8 doses a month is not recommended and tells doctors to consider stopping if darkening appears.

1 in 100 women at up to 8 doses a month, against nobody on a dummy injection. About 38 in 100 after 8 days of daily dosing, in a separate study without a comparison group.

Source [01]

Sudden liver inflammationSerious

She had taken 10 doses over a year. Her liver blood tests were more than 40 times the upper limit of normal and her bilirubin six times, and everything returned to normal four months after she stopped. No other cause was found, so the label says the drug's role could not definitively be excluded. There was no wider signal of liver harm in the programme.

One woman in the whole development programme, during the open-label year.

Source [01]

Harm to a pregnancySerious

In pregnant dogs, losses after implantation were three to eight times higher than in untreated animals at every dose tested, and no safe dose could be identified. In mice, the pups showed developmental delays. The label therefore tells women of childbearing age to use effective contraception while taking it and to stop as soon as they suspect they are pregnant. Of the 7 human pregnancies, five ended in full-term live births, one in a miscarriage and one was lost to follow-up, with no birth defects reported.

Not measured in people. Only 7 pregnancies occurred among more than 1,057 women treated for up to a year, which is far too few to tell.

Source [01]

Feeling sick

It starts within half an hour to an hour of the injection and lasts around two hours. It is worst the first time and much less common after that. Thirteen in 100 women took an anti-sickness medicine for it, and among those who did, later doses made them sick about a third as often. Eight in 100 women left the trials because of it, against nobody on the dummy injection. About 2 in 100 described it as severe.

40 in 100 women, against about 1 in 100 on a dummy injection.

Source [01]Source [03]

Flushing

A hot, red feeling in the face and chest. None of the episodes was serious and fewer than 1 in 100 were severe, but 1 in 100 women stopped the drug because of it.

20 in 100 women, against fewer than 1 in 100 on a dummy injection.

Source [01]

Reactions where the needle goes in

Pain, redness, bruising, itching and numbness at the site. The gap over the dummy injection is small, because sticking a needle in the belly or thigh causes most of this on its own.

13 in 100 women, against 8 in 100 on a dummy injection.

Source [01]

Headache

Usually mild, and 1 in 100 women stopped the drug because of it. One woman had a headache severe enough to put her in hospital.

11 in 100 women, against 2 in 100 on a dummy injection.

Source [01]

Blood pressure up, heart rate down

It peaks two to four hours after the injection and is usually back to normal within 12 hours. Taking two doses within 24 hours can add the effects together, which is why the label forbids it. This small, predictable rise is the reason the medicine is contraindicated in anyone with uncontrolled high blood pressure or known heart disease and not recommended for anyone at high cardiovascular risk — the effect itself is minor, the population it is minor in is healthy women in their thirties.

After every dose, in everyone, by a small amount: up to 6 mmHg on the top number and 3 on the bottom, with the pulse dropping by up to 5 beats a minute.

Source [01]

Vomiting

Almost always alongside the sickness rather than on its own — only about 3.5 in 100 women reported both together. One in 100 women stopped the drug because of it.

5 in 100 women, against fewer than 1 in 100 on a dummy injection.

Source [01]Source [03]

Pins and needles, dizziness, tiredness, a blocked nose

The small stuff, all of it more common on the drug than on the dummy injection and none of it serious in the trials. Nothing has been published about whether any of it persists, because nobody was followed after stopping.

Between 2 and 3 in 100 women each, against 0 to 1 in 100 on a dummy injection.

Source [01]

These are the amounts the studies below gave their participants, and they are here as facts about those studies. They are not a recommendation, not a starting point and not a range to pick from. What a person should take, if anything, is a question for a doctor who knows them.

The two trials the approval rests on — RECONNECT studies 301 and 302, low sexual desire causing distress in premenopausal women, against a dummy injection

1.75 mg injected under the skin of the belly or thigh by the woman herself, as needed, about 45 minutes before sex. No more than one dose in 24 hours.

24 weeks. The middle woman gave herself 10 injections in that time; most used it two to three times a month and no more than once a week.

Source [01]Source [04]Source [05]

The open-label year that followed both trials, in which everyone received the drug and knew it

1.75 mg under the skin, as needed, no more than 12 doses a month.

52 weeks. 684 of the 856 eligible women enrolled and 272 finished; the middle woman gave herself 12 injections over the year.

Source [01]Source [17]

The earlier dose-finding trial, which tested three amounts against a dummy injection and picked the one that went to the big trials

Three different amounts under the skin in separate groups, as needed, against a dummy injection. 1.75 mg was chosen for the phase 3 programme.

Up to 12 weeks, after a 4-week run-in period.

Source [03]Source [14]

The dedicated blood-pressure study, which gave it every day rather than as needed to find the ceiling of the effect

1.75 mg under the skin once a day, open-label.

8 days, followed by a period in which women were secretly reassigned to continue or stop. A separate study ran 8 more consecutive daily doses to look at skin darkening.

Source [01]Source [06]

The brain-scanning crossover study at Imperial College London, in which each woman received both the drug and a dummy injection

A single 1.75 mg injection under the skin, from the same autoinjector used in the trials.

One dose per visit, two visits per woman, with brain scans on the day and a follow-up question 24 hours later.

Source [09]

The early studies in men, by nasal spray and by injection, which never led to an approved product

Nasal spray at doses above 7 mg produced a measurable erectile response against a dummy spray; injections under the skin were tested from 0.3 to 10 mg.

Single doses, measured over a few hours in a clinic. The application to go on testing it in men in the United States was withdrawn in 2017.

Source [15]Source [16]

What people report

• Whether it does anything for women past the menopause — the two large trials excluded them and the label says it is not indicated for them. The one registered trial in postmenopausal women, an 8-week randomised study of the nasal spray in sexual arousal disorder that finished in 2007 (NCT00425256), has never posted results.
• Whether it does anything for men's sexual problems — the male programme was withdrawn in 2017 and no trial of it in men is registered.
• Whether it is better or worse than the tablet approved for the same condition — no trial has ever compared bremelanotide with flibanserin.
• Whether the benefit lasts beyond six months, because the 52-week extension had no dummy-injection group to compare against.
• Why 4 in 10 women on the drug left the trials early, and whether the ones who stayed were the ones it suited.
• Whether the questionnaires used to measure it capture anything that matters to a person — two peer-reviewed re-analyses say the validity evidence is thin, and the trial authors disagree in print.
• Why the count of satisfying sexual encounters rose in the mid-sized trial and then did not move in either large one.
• What it does to blood pressure in a woman whose high blood pressure is controlled with tablets — the dedicated blood-pressure study managed to recruit only two such women.
• Whether the darkened patches of skin and gums always fade after stopping — the label says resolution was not confirmed in all patients.
• What it does to a pregnancy in a person, as opposed to in dogs and mice, where it caused harm at every dose tested and no safe dose could be found.
• Whether it passes into breast milk — the 2019 label says there is no information at all, and a 10-woman study that finished in November 2025 has posted no results.
• What it does in anyone under 19 or over 56 — nobody outside that age range has been studied.
• What years of intermittent use do: the longest anyone has been followed is 18 months, and most of that was without a comparison group.
• Whether the small rises in LH, FSH and testosterone seen in 31 women mean anything, or have anything to do with the effect on desire.
• How it actually works — the approved label states in as many words that the mechanism by which it improves this condition is unknown.
• Whether it helps women whose low desire has an identifiable cause, such as another illness, a medicine or a relationship problem — all of them were excluded from the trials.
• What is in vials sold online as PT-141, which is a different question from what is in the licensed product.
• Whether the two other things it has been tested for go anywhere: a 108-person obesity trial alongside tirzepatide, now closed to recruitment, and a 16-person open-label study in diabetic kidney disease that finished in April 2024 — neither has posted results.

Does PT-141 work?

For the one thing it is approved for, it works a little. In two trials of about 1,200 women together, desire scores rose more on the drug than on a dummy injection and distress about low desire fell more, and about 6 in 10 women said the treatment had helped them — against about 3.5 in 10 who said the same about the dummy. But the number of satisfying sexual encounters did not change at all, and the average improvement in desire was smaller than the size of change the US regulator's own reviewers judged meaningful to a patient. It is a real effect that is easy to oversell.

Source [03]Source [06]

Is PT-141 legal?

It depends where you are and how you got it. In the United States it is a prescription medicine called Vyleesi, approved on 21 June 2019 and currently sold by Cosette Pharmaceuticals. In the European Union it is not an approved medicine at all — it does not appear anywhere in the EU's register of authorised medicines — so nothing sold as PT-141 in Europe is a licensed product. Buying vials online as a research chemical is a different thing again from being prescribed it.

Source [10]Source [12]

What are the side effects of PT-141?

The big one is feeling sick: 4 in 10 women in the trials, against about 1 in 100 on a dummy injection, usually starting within an hour and passing within two. Flushing affected 2 in 10, headache 1 in 10, and reactions where the needle goes in about 1 in 8. Blood pressure rises slightly after every dose and the pulse slows, which is why it is forbidden to anyone with uncontrolled high blood pressure or known heart disease. Used more often than the label allows it darkens patches of skin and gums, and those patches did not fade in everyone.

Source [01]

Does PT-141 work for men?

Nobody has properly tested that. In the early 2000s it was given to men as a nasal spray and as an injection, and a rigidity monitor recorded more erectile activity than after a dummy — but those were short clinic studies measuring a device reading, not whether anyone's sex life improved. The application to go on testing it in men in the United States was withdrawn in 2017 without a product, and there is no registered trial of it for a sexual problem in men. Anything sold to men as PT-141 today rests on that unfinished work.

Source [01]Source [06]Source [15]

PT-141 vs Viagra — what is the difference?

They work in completely different places. Viagra and its relatives act on blood vessels in the penis and help an erection happen once arousal has started; PT-141 acts on a receptor in the brain and is meant to affect desire itself. PT-141 is approved only for women who have not been through the menopause, and only for low desire, not for erections. No trial has compared the two, and the one published study that gave them together was a 19-man crossover measuring a rigidity monitor.

Source [01]Source [21]

PT-141 vs Addyi (flibanserin) — which is better?

Nobody knows, because no trial has ever compared them. A search of the US trials registry on 3 August 2026 for studies naming both returned zero. They are used very differently: Addyi is a tablet taken every night and PT-141 is an injection taken before sex, and the two were measured on the same desire and distress questionnaires but in separate trials, which is not a fair comparison. Anyone claiming one beats the other is not citing a study.

Source [06]Source [22]

Can you buy PT-141?

In the United States, with a prescription, as Vyleesi. In the European Union there is no licensed product to buy, because it has never been approved there. Vials sold online as PT-141 for research are outside all of that: nobody has checked what is in them, and unlike several other peptides it is not even on the US regulator's list of substances nominated for pharmacies to compound. This register does not link sellers and does not tell anyone how to use anything.

Source [02]Source [10]Source [23]

How long does PT-141 take to work and how long does it last?

The label says to inject at least 45 minutes before sex, and it also says, in as many words, that how long the effect lasts after each dose is unknown. The drug itself peaks in the blood about an hour after the injection and half of it is gone within about three hours. In one small study in 31 women, more of them reported higher desire a full day later after the real injection than after the dummy one. In the big trials, the difference on the monthly questionnaires showed up by week 4 and barely grew after that.

Source [01]Source [09]

Does PT-141 make you tan?

It darkens skin in patches rather than tanning it evenly, because it switches on the same receptor the body uses to make pigment. Used within the label's limit of 8 doses a month it happened to 1 in 100 women and to nobody on a dummy injection. Given daily it happened to about 38 in 100 women after 8 days, on the face, the gums and the breasts, and more often in women with darker skin. The label states the patches were not confirmed to fade in everyone after stopping.

Source [01]

Is PT-141 the same as Melanotan II?

Almost, and the difference matters. Both are the same small ring of amino acids built on the body's own pigment hormone; bremelanotide ends in a free acid where Melanotan II ends in an amide. That one change is the whole difference between an approved medicine with a public label and 1,200 people's worth of trial data, and a compound that has never been approved anywhere and is sold for tanning and libido with no controlled trial behind it. They are not interchangeable and the evidence behind them is not comparable.

Source [01]Source [13]

Is PT-141 banned in sport?

No. The 2026 World Anti-Doping Agency prohibited list does not name bremelanotide, PT-141, melanotan or melanocortin anywhere in its text, and it does not belong to any of the listed classes. The catch-all category for unapproved substances does not capture it either, because that category applies only to substances with no approval from any government health authority, and this one has been approved in the United States since 2019. Melanotan II, which is nearly the same molecule, would be caught by that category precisely because it has never been approved.

Source [11]Source [12]

Why is PT-141 not approved in Europe?

The honest answer is that we do not know, because there is nothing to read. The EU's register of authorised medicines contains no bremelanotide and no Vyleesi, and the European Medicines Agency has published no assessment of it — no approval, no refusal, no withdrawn application. That is different from the case of a medicine Europe looked at and turned down; here there is simply no European file at all. Anything sold as PT-141 in Europe is therefore an unlicensed product whatever the seller calls it.

Source [10]

1. [01]VYLEESI (bremelanotide injection) US prescribing information — indication, contraindications, adverse reaction table (nausea 40.0% vs 1.3%), blood pressure, focal hyperpigmentation, section 11 structure Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys)-OH, section 14 tables 2 and 3 (2019)
2. [02]VYLEESI (bremelanotide) injection, current US label, DailyMed — Cosette Pharmaceuticals, published 18 November 2025 (2025)
3. [03]Kingsberg and colleagues, bremelanotide for the treatment of hypoactive sexual desire disorder: two randomized phase 3 trials (Obstet Gynecol 2019;134:899-908; 1,267 randomised, responder rates 58.3/58.2% vs 36.1/35.4%, satisfying sexual events p=.764 and p=.702) — free full text (2019)
4. [04]RECONNECT study 301 (NCT02333071, 723 participants, completed, results posted; FSFI-desire +0.54 vs +0.24, FSDS-DAO item 13 -0.73 vs -0.36) (2016)
5. [05]RECONNECT study 302 (NCT02338960, 714 participants, completed, results posted; FSFI-desire +0.63 vs +0.21, FSDS-DAO item 13 -0.71 vs -0.42) (2016)
6. [06]FDA multi-discipline review and evaluation, NDA 210557 Vyleesi — benefit judged "modest", the 1.2-point meaningful-change threshold, the ambulatory blood pressure review, and IND 61706 for the male erectile dysfunction indication recorded as withdrawn in 2017 (2019)
7. [07]Spielmans, re-analyzing phase III bremelanotide trials for hypoactive sexual desire disorder in women (J Sex Res 2021) — odds of stopping for a side effect 11.98 times higher (95% CI 3.74-38.37); rebutted by Kingsberg and colleagues in the same journal (2021)
8. [08]Clayton and colleagues, safety profile of bremelanotide across the clinical development program (J Womens Health 2022) — 70% of the bremelanotide group entered the open-label extension against 87% of the placebo group (2022)
9. [09]Thurston and colleagues, melanocortin 4 receptor agonism enhances sexual brain processing in women with hypoactive sexual desire disorder (J Clin Invest 2022; randomised double-blind crossover, 31 women; 21 of 31 reported increased desire after bremelanotide against 8 of 31 after placebo) — free full text (2022)
10. [10]Union Register of medicinal products, European Commission — the complete file of centrally authorised human medicines, updated 31 July 2026, containing no bremelanotide and no Vyleesi (downloaded and searched 3 August 2026) (2026)
11. [11]WADA World Anti-Doping Code International Standard, Prohibited List 2026 — full text searched 3 August 2026: no occurrence of bremelanotide, PT-141, melanotan or melanocortin; S0 covers only substances with no current approval by any governmental regulatory health authority (2026)
12. [12]Drugs@FDA, NDA 210557 — original approval 21 June 2019, prescription, current sponsor Cosette (2019)
13. [13]PubChem CID 9941379, bremelanotide — C50H68N14O10, 1,025.2 g/mol, CAS 189691-06-3, IUPAC name showing D-phenylalanine and the (2->7) lactam ring
14. [14]Phase 2b dose-finding trial in premenopausal women (NCT01382719, 612 enrolled and 397 randomised, completed, results posted; satisfying sexual events was the primary endpoint, +0.8 on the highest dose vs +0.2 on placebo) (2012)
15. [15]Diamond and colleagues, double-blind, placebo-controlled evaluation of intranasal PT-141 in healthy males and patients with erectile dysfunction (International Journal of Impotence Research) (2004)
16. [16]Rosen and colleagues, safety, pharmacokinetics and pharmacodynamic effects of subcutaneously administered PT-141 in men with erectile dysfunction (International Journal of Impotence Research) (2004)
17. [17]Simon and colleagues, long-term safety and efficacy of bremelanotide for hypoactive sexual desire disorder (Obstetrics and Gynecology, free full text) (2019)
18. [18]Physiological study of the role of the melanocortin-4 receptor in brain activity in women with HSDD (NCT04179734, 40 enrolled, completed, results posted) (2020)
19. [19]Spielmans, small effects, questionable outcomes: bremelanotide for hypoactive sexual desire disorder (Journal of Sex Research) (2024)
20. [20]Kingsberg and colleagues, failure of a meta-analysis: a commentary on Glen Spielmans's re-analysis (Journal of Sex Research) — the trial authors' rebuttal (2021)
21. [21]Diamond and colleagues, co-administration of low doses of intranasal PT-141 and sildenafil to men with erectile dysfunction (Urology, 19 patients, crossover) (2005)
22. [22]ClinicalTrials.gov API v2 search for studies naming both bremelanotide and flibanserin: totalCount 0 (checked 3 August 2026)
23. [23]FDA, bulk drug substances nominated for use in compounding under section 503A, updated 14 May 2026 — bremelanotide and PT-141 absent (2026)